Conventionally, a printing apparatus for printing using a ultraviolet (UV) ink which is cured by UV light irradiation is known. This printing apparatus ejects an ink from a nozzle of a head to a medium, and irradiates a UV light on a dot formed on the medium. By UV light irradiation, the dot is cured and settled on the medium, so good printing may be enabled for a medium which is less prone to absorb a liquid. This printing apparatus is disclosed in, for example, Patent Literature 1.
Patent Literature 1 discloses a printing apparatus including a conveyor unit for conveying a print medium, six heads arranged in a conveying direction to respectively eject color inks of cyan, magenta, yellow, black, orange, and green, six pre-curing irradiation units placed at a downstream side in the conveying direction between each head for pre-curing (peening) a dot ink ejected on the print medium from each head, and a curing irradiation unit for curing the dot ink to settle the dot ink on the print medium. The printing apparatus disclosed in Patent Literature 1 performs two-steps curing of pre-curing and curing, on the dot ink to prevent a blurred color ink or dot expansion.
The pre-curing irradiation unit disclosed in Patent Literature 1 is placed above the print medium and irradiates a UV light on the print medium, hence it is a so-called UV light irradiation device, and irradiates a UV light of a line shape in a widthwise direction of the print medium. In response to a request for a lightweight and compact design of the printing apparatus itself, the pre-curing irradiation unit uses a light emitting diode (LED) as a light source, and a plurality of LEDs is arranged side by side along the widthwise direction of the print medium.
As described above, in the case where an LED is used as a light source, there is a degradation problem of light emitting efficiency and life caused by heat generated from the LED itself in that most of the power supplied is converted to heat. Also, like the pre-curing irradiation unit, in the case of an apparatus having a plurality of LEDs mounted therein, this problem is more serious in terms of the increased number of LEDs acting as a heat source. By this reason, a light irradiation apparatus using an LED as a light source is generally configured to inhibit the heat generation of the LED using a cooling structure such as a heat sink (for example, Patent Literature 2).
The light irradiation apparatus (light source apparatus) disclosed in Patent Literature 2 includes a plurality of LEDs, radiators thermally coupled to the LEDs respectively, and a fan that sends a cooling airflow along an arrangement direction of the radiators, and efficiently cools the radiators (i.e., the LEDs) by the airflow generated by the fan.